Method for optical measurement of the three dimensional geometry of objects

Abstract

The invention relates to a method for optically scanning the three-dimensional geometry of an object by means of triangulation, in which a pattern (9, 9′) is projected onto the object (7) to be scanned in order to obtain a 3D data set, and the projected pattern (9, 9′) is recorded in an image (40, 41). In a first step for the production of at least one first image (40), a first pattern (9) is projected and in a second step for the creation of at least one further image (40), a further pattern (9′) deviating from the first as regards position or shape is projected onto the object (7) to be scanned and the image (41) is created. The first image (40) and the further image (41) comprise at least one common point (44). The 3D data acquired from the images (40, 41) are merged in a subsequent step on the basis of the 3D data of the at least one common point (44) such that the 3D data acquired from said images (40, 41) agree at least with reference to the 3D data of the common point (44) in the 3D data set.

Description

TECHNICAL FIELD[0001]The invention relates to a method for optical measurement of the three dimensional geometry of objects and is concerned with the problem of camera-shake induced in 3D data of scanned objects acquired using stripe projecting methods and with the task of 3D scanning when there is relative motion between the camera and the object when being scanned, particularly for dental purposes.PRIOR ART[0002]Digital design data for the computer-assisted production of dental prosthetic items without having to create the usual impression can be acquired by optically scanning one or more teeth in a patient's mouth.[0003]For such scanning, use is frequently made of measuring methods based on the principle of triangulation. Phase-shifting triangulation is disclosed in EP 0 160 797, in which a three dimensional data set is acquired from a sequence of images of a pattern which is displaced from image to image.[0004]With prior triangulation methods, a single straight stripe of light i...

AI Technical Summary

Benefits of technology

[0031]The advantage of assigning by counting and using the binary code method resides in the fact that the 3D data for the area illuminated by the pattern can be generated immediately after each individual exposure.

[0102]The redundant data should be such that the demands on memory storage and the time required for data acquisition are both minimized by using the least possible amount of data to give the highest possible degree of correlation between the individual images.

Problems solved by technology

Since the change in the orientation between camera and object is, however, unknown, the two-dimensional patterns of the images Pi cannot be correctly merged to form a common 2-dimensional pattern of the overall image, which, for example, is chosen so as to be the same as the coordinate system of the first exposure.

When the relief data contained in the lines of the 2-dimensional patterns of the blurred individual images are merged to form a common 2-dimensional pattern, an erroneous surface structure of the object being scanned will be obtained.

The present problem is to provide a method for creating a three-dimensional image of an object being scanned, particularly for dental purposes, which produces a sufficiently accurate 3D model even if camera-shake takes place.

Images